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Curl_sasl_create_digest_md5_message: fix buffer overflow

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When negotiating SASL DIGEST-MD5 authentication, the function
Curl_sasl_create_digest_md5_message() uses the data provided from the
server without doing the proper length checks and that data is then
appended to a local fixed-size buffer on the stack.

This vulnerability can be exploited by someone who is in control of a
server that a libcurl based program is accessing with POP3, SMTP or
IMAP. For applications that accept user provided URLs, it is also
thinkable that a malicious user would feed an application with a URL to
a server hosting code targetting this flaw.

Bug: http://curl.haxx.se/docs/adv_20130206.html
This commit is contained in:
Eldar Zaitov 2013-01-30 23:22:27 +01:00 committed by Daniel Stenberg
parent add37cc49f
commit f206d6c055
1 changed files with 6 additions and 17 deletions
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23
lib/curl_sasl.c
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@ -346,9 +346,7 @@ CURLcode Curl_sasl_create_digest_md5_message(struct SessionHandle *data,
snprintf(&HA1_hex[2 * i], 3, "%02x", digest[i]);
/* Prepare the URL string */
strcpy(uri, service);
strcat(uri, "/");
strcat(uri, realm);
snprintf(uri, sizeof(uri), "%s/%s", service, realm);
/* Calculate H(A2) */
ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
@ -392,20 +390,11 @@ CURLcode Curl_sasl_create_digest_md5_message(struct SessionHandle *data,
for(i = 0; i < MD5_DIGEST_LEN; i++)
snprintf(&resp_hash_hex[2 * i], 3, "%02x", digest[i]);
strcpy(response, "username=\"");
strcat(response, userp);
strcat(response, "\",realm=\"");
strcat(response, realm);
strcat(response, "\",nonce=\"");
strcat(response, nonce);
strcat(response, "\",cnonce=\"");
strcat(response, cnonce);
strcat(response, "\",nc=");
strcat(response, nonceCount);
strcat(response, ",digest-uri=\"");
strcat(response, uri);
strcat(response, "\",response=");
strcat(response, resp_hash_hex);
snprintf(response, sizeof(response),
"username=\"%s\",realm=\"%s\",nonce=\"%s\","
"cnonce=\"%s\",nc=\"%s\",digest-uri=\"%s\",response=%s",
userp, realm, nonce,
cnonce, nonceCount, uri, resp_hash_hex);
/* Base64 encode the reply */
return Curl_base64_encode(data, response, 0, outptr, outlen);